Preheat oven to 160 degrees celsius.
Mix crushed biscuits and melted butter together in a mixing bowl, then pour the mixture into a pie tin and spread evenly to create the pie base. Place base in the fridge for 30 minutes.
Meanwhile, combine condensed milk, lemon juice and zest in a mixing bowl. Then add the egg yolks and beat well to mix all the ingredients together.
Pour the lemon mixture over the biscuit base and bake for 12 minutes. When the lemon mix is cooked, take the pie out of the oven and allow it to cool slightly, but don’t turn the oven off yet!
Whisk the egg whites and a pinch of salt in a mixing bowl until soft peaks form, then slowly add the sugar and continue beating until the peaks are firm.
Spoon (or pipe) the meringue mix onto the pie and bake for another 10 minutes, or until the meringue is light and golden in colour.